Should I expect to find more than one Space-A roster on a base?

No. Only one Space-A roster shall be maintained on a base, installation or post. The maintenance of such a roster is the responsibility of the AMC passenger or terminal service activity. If there is no AMC transportation activity, then the base, installation or post commander designates the agency responsible for maintaining the Space-A roster. You may find an exception at locations where a second service has a separate facility such as Andrews AFB and the Washington NAF.